Finally got around to taking me sons 2002 DT125R out for a shake down run before im happy to let him out on it after the winter strip n rebuild.
Cold on tick over its putting out a lot of smoke which i kinda expected as the engine has had a full strip and rebuild including new top end rebore piston, rings, conrod big ends etc. But after 5-6 miles and up to temperature its still smoking like vape addict on steroids.
When i got it back the rear end of the bike was covered in loads of black unburnt oil and it was still smoking just as bad on tick over. The bike had a Gianelli full system on before strip down and this has been replaced with a full DEP system. The old exhaust was full of oil when i left it standing and made a nice mess as it leaked out on the garage floor over the past few months.
I fitted a new throttle cable as part of the restore and noticed a fair bit of slack on the cable where it connects onto the oil pump and if i did'nt know better would say the oil pump return spring is worn as it does'nt snap back to fully closed. The cable has been set up as per the Haynes book.
As its still being run in i tried not to take it past 5k but the hooligan in me let it run up to 7k in 4th & 5th where it should be in the power but it just splutters like a good un. The engine pulls really strong from low revs and i was quite surprised how smooth it is
Things i have'nt done yet is strip/check the carb as it seamed to be running ok before strip down. And the bike fired up no problem when rebuilt.
I dont know if the main jet (240 std ) has been changed to allow for the exhaust. And a check of the new plug only indicates that its oily very oily and it does'nt have enough miles on it to show a true refection of what shade it should be.
Before i check the carb does anyone have any ideas ?
Can the oil pump be putting out too much oil even on tick over ? Can you get an oil pump repair kit for these ? And if main jet is wrong ( Possibly standard and too small ) will replacing this and or raising the needle 1 notch help burn more fuel to help burn the oil ?
The bike is running standard airbox and plug is BR9ES
@Scootjockey I had a similar issue on my 4DL Engine years back. Just WAY too much oil put out even though the pump was set up according to manufacture. I just decided that maybe the pump had failed and removed it and went premix, been that way ever since.
The one thing I would suggest is just double check the oil you're using is designed for injection and not premix.
MX Oils are too rich and therefore not appropriate.
What’s in the fuel tank? Maybe drain & replace with new petrol?
If it’s splattering the bike from the tailpipe with a new exhaust I’d definitely suspect the autolube. Personally I’d disconnect the oil lube cable and oil to inlet-manifold, & block the oil inlet hole, temporarily. Try running it on a small amount of premix in the tank. If it runs well, it’s your auto lube. If it doesn’t try running it up to temp with no gear oil.
It will be one or the other by the sounds of you oily plug and rear end! ...
Hi Callum I’ve changed the oil pump and it’s running much better. Looks like the return spring has stretched or jumped past the stop once or twice. But when I had a close look either something has snapped inside and made its way out of the oil input connection or something has forced its way in, possibly deliberately? I don’t know but you can rotate the cable pulley and it will just sit where it likes. The new one snaps shut and has a strong spring mechanism.
Thanks for all the suggestions. Gonna take it for a run and see if it runs without spluttering. Hope fully I’ll be able to get some miles on it then do a plug check
@SpookDog Hi the new oil pump done the trick with the bike running much better and not splattering everything behind it in oil or smoke.
So I took it for a run to put some extra miles on it respectfully trying not to lash it and only letting it run up to 7-8k to do a plug chop.
Only for it splutter and not go past 8k then when it did get there it died as if the throttle was part closed just for it to drop out of the power. Down a cog and came back to life but it didn’t like going upto or past 8k. The drive back got me thinking and I give it handful to see if it would pull past 8k but it just wasn’t having it.
Got home checked the plug and if anything it was rather black running more rich than the coffee colour I was hoping for. Only one thing for it carb off and have a look.
To my disgust the carb was filthy the float and bowl covered in yellow silt. Striped the jets to find the main jet must have spent its life in the bottom of a tool box it was that battered and bruised I couldn’t make out what size it was. Naive as I am I still knew over the years Yamaha will have changed the carbs and fuelling and the Haynes manual confirmed this. The magnifying glass tool on my iphone confirmed 125 main jet with 5J25 Needle on the 4th step. Ahem that should be 210 main jet not 125 ! Or it’s the wrong carb ?
A visit to the local MX shop made me £12 lighter and got me some nice shiny brass in the shape of 200,210,220,230 jets. I hoped I didn’t need them all but it’s better to be safe.
Cleaned the carb and fitted the 210 main jet and took it for a run, once up to temperature it ran like a dream. I know it sounds ironic but even the engine tone sounded happier more powerful and deeper….. Pulls well in all gears and no splutters or flat spots up to and past 8k. Quick plug chop later and conformation of the nice colour I was looking for.
So all is looking good and it just needs a few more miles on it and hopefully my Son will be abusing it and annoying the neighbours just like I did all those years ago.
So job done another DT back on the roads and not some industrial estate or school field being chased by the Feds.
@Scootjockey the 2002 full power European model comes with a 240 main jet as standard, the restricted UK version has a 210. Is yours restricted? Also you seem to have the wrong idea of what a plug chop is. It's performed with a brand new plug. You don't ride around for any length of time, (no more than about 20 seconds) you then remove the plug and put your old one back in for the short ride home, (or push it back) and most importantly, you then take a hacksaw and 'chop' it. This video explains exactly how to do a plug chop. The chop is performed at around 8 minutes but I highly recommend watching the entire video.
@markus-w Hi the bike is a 2002 model 2003 plate French import 4BL chassis and engine numbers. 3MB00 Barrel and what looks like 3RM02 Carb. Once up to temperature I nailed it in 3rd 4th and 5th up to 8k Hit the kill switch pulled the clutch in and freewheeled to stop. Popped the plug out and checked the colour.
I’m not aware of it being restricted ?
Fit a 240 main jet. I’m betting you have a .25 pilot jet (or should have) It made a lot of difference to engine note & temperament when I changed up from a 210 to the proper size...
Did you remove & clean the emulsion/needle jet tube? Mine was packed with silty-sand that blocked the holes. Also make sure the power jet is clear?...
I’ve had similar problems in the past with my full power 3rm02 carb’d bike. Make sure you bring the whole engine up to temp properly, not just the the top-end. Do a 15mile ride & keep to 6k running in!
@Scootjockey well you shouldn't warm the plug up, should be brand new. and the clue is in the name 'chop'. Get a hacksaw and cut off the threaded part so you can read the white porcelain bit underneath. As I said, all is explained in the video.
From memory it is .25 pilot jet and yes I cleaned the emulsion tube. To be honest these weren’t that too bad just the bottom of the float bowl and floats were covered in a yellow silt. Which rubbed off fairly easily with some carb cleaner. I don’t have a 240 main jet yet and I’m waiting for his majesty’s finest to drop a set of assorted jets through the letter box. I took it out this morning to get some miles on it only taking it up to 5-6.5k. And it’s running nice I’m still very surprised how smooth it is.
You need a 240 main jet then bud. It made a big difference when I upped mine from a 210, even though I thought it was fine before. I’d only use Mikuni Jets as well, maybe EBC at a pinch. I wouldn’t trust anything other than Mikuni really though...
Good luck with the bike. When they’re running proper they’re like nothing else. Full power 3mb dtr’s Are sweet
@SpookDog they are okay, but there are a lot of damn sight better bikes. My ETX is dog slow, but the MX/RX/SX are lovely. Just a simple matter to convert mine.
The nice thing about DTs is they are dependable. I don't think my DT has ever let me down! It's gone wrong, but it has always got me home!
I couldn’t find a Mikuni 240 jet for sale outside of the US of A! My bike seemed to run fine on a 210, but only in comparison to how it had run before, it had a 180 in it! With a 240 it really came alive in mid range torque (remember, it’s all comparative!)
I’m actually very interested in what your Dtr revs out to @ in gear, under load. I seem to reach my usable ceiling @ 7-8K
Now there’s some miles on it We’ve been opening it up a bit. Still running Kmh clocks and I kinda know they will be out but with me pushing 14 stone that’s close to 90kg in new money with jacket helmet boots n gloves it’s revving out in 5th and pushing 9.5k in top well into the 120-130kmh. So I’m well happy. One thing I am really pleased about is it’s still pulling past the power through the gears and it didn’t drop past 8k with a bit of an incline. I’m sure if I was 17 again weighing in at 10 stone wet it would be well into the red.
The exhaust tone from the full DEP just makes you want to blast it everywhere